Hydrofining followed by heat stabilizing



March 15,1960 J. VAN DYCK FEAR 2,928,787

HYDROFINING FOLLOWED BY HEAT STABILIZING Eile d Nov. 28, 1956 t BBSQQm cotccuuohgz INVENTOR. JAM ES VAN DYCK FEAR Wm, q

ATTORNEY HYDROFINING FOLLOWED BY HEAT STABILIZING James Van Dyck Fear, Media, Pa., assignor to Sun Oil Company, Philadelphia, Pa., a corporation of New Jersey This invention relates to refining petroleum by hydrogenation.

The invention provides a novel manner of producing refined petroleum products by catalytic hydrogenation. The products obtained according to the process of the invention have highly satisfactory properties for various uses, for example as transformer oils, cable oils, refrigerator oils, waxes, etc.

The process of th'invention involves, first, catalytic hydrogenation under condi.ions providing conversion of nonhydrocarbon constituents of the petroleum charge stock, and producing a product having improved oxidation stability and other properties. Under the conditions employed to obtain these results, relatively nonvolatile corrosive sulfur-containing material is also produced, apparently by conversion of sulfur compounds in the charge stock. This sulfur-containing material is thought to be elemental sulfur, though the invention is not to be limited by any theory.

The process of the invention further involves subjecting the hydrogenation products to a heat treatment in the absence of hydrogenation caialyst. The purpose of the heat treatment is to convert the corrosive sulfurcontaining material into noncorrosive sulfur compounds. The latter compounds are not only noncorrosive but also generally exhibit advantageous oxidation inhibiting properties.

In the heat treatment, the liquid hydrogenation products are passed continuously through a soaking system containing obstructions to the flow of the liquid hydrogenation products. The obstructions cause the liquid products to undergo sufiicient pressure drop that thermal currents are avoided. The obstructions in the soaking system are essential, since in continuous passage through an ordinary unobstructed soaking vessel, thermal currents in the flowing liquid cause nonuniform residence time of liquid in the soaking system. Portions of the liquid therefore frequently do not remain in the soaking system sufiiciently long to undergo complete removal of corrosive sulfur. This invention solves the problem, since the liquid does not flow backward past the obstructions, and thermal currents are limited to small portions of the soaking system.

The heat treatment according to the invention is carried out in continuous fashion. Such operation provides better control of the process conditions, and a generally superior product as a result of better control ofthe residence time.

The temperature of the oil during passage through the soaking system is Within the approximate range from 450 F. to 650 F. Lower temperatures generally do not provide satisfactory conversion of sulfur-containing material. Higher temperatures generally result in thermal degradation and discoloration ofthe hydrogenation products.

The total residence time of hydrogenation products in the soaking system must be long enough to provide satisfactory conversion of sulfur-containing material, but not atent 0* g 2,928,787 Patented Mar. 15, 1960 so long as to result in excessive thermal degradation and discoloration of the hydrogenation products. The exact limits of residence time to provide these results vary with many factors including the temperature in the soaking system, the nature of the hydrocarbons treated and the desired properties of the ultimate product. In some inbetween soaking zones can be employed in place ofrthe stances, particularly where relatively high temperatures are used in the soaking system, the residence time must be controlled within close limits in order to obtain the optimum combination of conversion of sulfur and avoidance of thermal degradation. In any event, it is important that the difference between the residence time of the portions which remain in the soaking system the longest time and the residence time of the portions which remain the shortest time, i.e. the difference between the maximum and minimum residence times, should be as small as possible, in order to give the optimum combination of corrosive sulfur elimination and avoidance of degradation.

The average residence time in the soaking systemwill usually be within the approximate range from 5 to minutes. minutes. Generally, relatively short residence times are employed in conjunction with relatively high temperatures and vice versa.

The soaking system through which the hydrogenated oil is passed in the process according to the invention contains obstructions which provide, in at least one intermediate location in the soaking system, a free space for travel of hydrogenated oil which has cross-sectional area not more than 0.75 times, and preferably not more than 0.5 times, the cross-sectional area which would be avail able at that level'in the absence of the obstruction. Any

suitable lesser proportion which does not result in ex- 7 cessive pressure drop can be employed.

ing system comprises a pluralityof soaking zones in series, each adjacent pair of soaking zones being connected by a .relatively constricted passageway. In this embodiment, the flowing liquid, in passing from a relatively expanded soaking zone into a relatively constricted connecting passageway, encounters the obstruction which provides the benefits of the invention. In this embodiment, the number of soaking zones in the soaking system can be two or more. Generally, greater numbers of zones provide greater uniformity in residence time. Since the liquid undergoes substantial pressure drop in passing through the constricted passageways between the soaking zones, greater numbers of the latter generally resultin greater total pressure drop. Since the smallest pressure drop which gives sufiiciently uniform residence time is preferred, the number of zones is preferably not greater than 10.

Preferred apparatus for use according to this embodiment of the invention comprises a vertically elongated vessel having therein one or more horizontal perforated plates. The perforations constitute the constricted pas-. sageways separating the soaking zones above and below the plate. Preferably, the total perforation area-constitutes not more than 50 percent of the cross-sectional area of the vessel at the level of the plate, so that the available cross-sectional area for passage of liquid through the plate is not more than 50 percent of the available. area for suc h passage in the soaking zones. The total perforation area may constitute any desirable lesser proportion than 50 percent of the cross-sectional area, any lesser proportion, e.g. down to 0.5 percent or less, that does not give excessive pressure drop being generally satisfactory. g Y

Other means for providing constricted passageways Preferably the time does not exceed about 30 perforated plates previously described. Thus, for ex ample, a series of vessels constituting the soaking zones, with connecting pipes constituting the constricted passageways, can be employed. This arrangement -corre-: sponds generally to a vessel containing a perforated plate having only one perforation th'erein. Perforated plates containing a plurality of'perfcrationsfelg. 10 to 1 00, are preferred in that they provide generally "superior results. i

ther means of providing obstructionsfin the soaking system can be employed. Thus, for example, transverse baffles extending across a portion of the cross section of asoaking vessel can be employed. plurality of such bafiies' arranged in such tnanner that-the fiowin'g liquid is obliged to follow a tortuous path can be ernployed-if desired.

It is also within 'the scope of "the iinve'ntion to employ "a soaking vessel containing "a 'noniadsorbent packing material, thepackingmaterial providing the obstructions and eliminating thermal currents. The 'packingshould be non'a'dsorbentin 'o'rder to-avoi'cl undesirable adsorption of the sulfur compounds formed in the heating. Any nonads'orbent packing material as known in the art, e.g.

I Raschig rings, etc., can be employed.

The use of a plurality of soaking zones "such as cylindrical vessels or portions thereof,-interconnectedby constricted passageways, is generally preferred to the use of a packed vessel, since in the latter casea larger vessel is require'd for a given throughput.

The passage of liquid through the soakingfsystem preferably in a substantially vertical direction, though other directions of fiowQsuch as horizontal, are within the scope of the'invention.

The'charge stock for the process according to' the invention is preferably a distillate petroleum fraction having A.P.I. gravity of from 20 to 40 and boiling range at least as high as that of gas oil. :Gas oil, lubricating oil, and wax distillates-are examples of'the preferred charge stocks according to the invention. Crude petroleum or residues can'also be treated according to the invention.

Preferred conditions for use in the hydrogenation step according tothe invention are temperatures in the approximate range from 500 F. to 800 F., mo'repr'eferably 650 to F. to 750 F.,jand pressures in the approximate range from 100 to 2000 p'.s.i.g.,mo're preferably 1000 to 2000 p.s.ig. However, any "conditions which result in a product containing corrosive sulfur containing'material may be involved in the first step. The inventio'n is generally applicable to those"situationswhere in'the'desired hydrogenation conditions for generalpur poses result in the specific concurrent result'of forming corrosive sulfur containing material.

A typical manner of performing the hydrogenation is bypassing the charge through a stationary bed of solid hydrogenation catalyst in the'presence of hydrogen, the space velocity being 0.25 to volumes of charge per volume-of catalyst bed per hounand the hydrogen consumption to 500 standard cubic feet per barrel of charge. Other known manners of performing the hydrogenation can be employed. Typical'catalysts arevarious metals or oxides or-sulfides thereof, such metals being 'forexample cobalt, iron, nickel, manganese, chromium, molybdenum, ma nesium, platinum, copper, "zinc, vanadium, etc. Typically, the catalyst is associated with a-suitable base or support, eig. bauxite, alumina, silica gel, clay, silica-alumina composites, kieselguhr, pumice, charcoal, activated carbon, aluminum silicates, etc. The well known-hydrogenation catalysts for mineral oils are suitable as a class for use according tothe invention.

The'following example-illustrates the invention. The example will bc des'cribe'd =with'referenceto the attached drawing which illustrates one embodiment 'of'the invention.

-A spetroleum distillate,= e;g. a -naphthenic lubricating an distillate having A.P..I. gravity of 25, is hydrogenated in zone 10 at a temperature of about 675 F. and pres sure of about 1500 p.s.i.g., by passing the oil downwardly through a stationary bed of solid hydrogenation catalyst comprising about 20 percent molybdinum sulfide on an alumina base, the liquid hourly space velocity being about 0.5 volume of oil per volume of catalyst bed per hour.

Oil is introduced through line 11 into zone 10, and hydrogenated oil is withdrawn through line 12 into high pressure separator 13, which may suitably operate at approximately the same pressure as the hydrogenation vessel. Gaseous and vaporous material including unreacted hydrogen is recycled, after suitable treatment for H 8 removal and light hydrocarbon removal if desired, through line 14 to zone 10. Makeup hydrogen is supplied through line 15 as needed. Liquid hydrogenation products are introduced through line 16 into 'low pressure separator 17, which may suitably operate at atm'o'spheric pressure. Gaseous and vaporous material is withdrawn through line 18. Liquid products are withdrawn through line 19, cooled by suitable means not shown to a temperature of 550 F. for example, and passed downwardly through soaking vessel 20. Vessel 20, which constitutes the soaking system, contains a plurality of plates 21 having perforations such as the perforation indicated by the "numeral 22.

The space velocity of the liquid oil in passing through vessel 20 is 6"volumes of 'oil per volume of vessel 'per hour, thus providing an average residence time of.10 minutes in vessel 20, or an average residence time in each 'of the soaking'zones 23 of 2 minutes. The necessary minimum residence time in vessel 20is for example about 9 minutes, in order to obtainfreedom'from corrosiveness tocopper. The'lowestresidence time of any portion of the liquid in vessel 20 is greater than '9 minutes. However, if the vessel 20 did not contain the piates 21, thelowest residence time would, because of the thermal currents and resulting inequalities of residence time, be less than 9 minutes, though the average residence time would still be 10 minutes. Thus, operation under-generally similar conditions except that the perforated plates 21 are omitted from vessel 20 results in a corrosive oil, indicating incomplete conversion of sulfur-containing material.

The oil removed through line 24 is cooled toiroom temperature bysuitable means not'shown. If desired, the cooling of this oil and of. the oil in line "19 can'be effected by indirect heat'exchange with the chargeoilin line '11. The product oil is steam stripped by means not shown to'rem'ove dissolved hydrogen sulfide.

The stripped product oil is free from corrosivity towards copper, as determined for example by immersing a copper strip, polished to A.S.T.M. standards, in the oil at 212" F. for 3 hours, and then examining'the'strip for stain. The oil'also'has improved oxidation stability, as a result of the hydrogenation and also .of .the production of oxidationinhibiting sulfur compounds.

The corrosive sulfurcontaining material which is formed in the hydrogenation'is,because of its lo'wv'olatility, not strippable from the hydrogenation fprodu'cts. Therefore, stripping of hydrogen sulfide fromthehydrd genation products, without previous passage through the soaking system, produces a corrosiveoil. 'In thesoaking system, the corrosive sulfur-containing material is'thought to be converted in part to hydrogen sulfide and in part to'organicsulfur compounds, thoughthe invention isnot to belirnite'd by'any theory. The hydrogen sulfide can be removed by. subsequent stripping to obtain a noncorrosive oil, the'remaining organicsulfur'compoundslbeing non'corrosive and often having oxidation-inhibiting,,properties.

' T he soaking operation according to thelinventio'n can oeperformed if desired at elevated pressure, forexampl by introducing the elhuent "16" from the separator 13 "directly into vessel 20, the effiuent 24 being introduced into separator 17.

The overall ratio of length to major dimension of the relatively expanded, or soaking zone portions, of the soaking system according to the invention is preferably within the approximate range from 1:1 to 50:1 for the overall soaking system. Thus, the ratio of length to diameter of the vessel 20 in the drawing is preferably within the indicated range.

The invention claimed is:

1. Process for producing improved petroleum products which comprises: catalytically hydrogenating a petroleum charge stock to produce a refined product containing relatively nonvolatile corrosive sulfur-containing material; separating the refined product from the hydrogenation catalyst; and passing a stream of the separated refined product in liquid phase at 450 F. to 650 F. continuously through a soaking zone, distributing said liquid stream in an expanded area in said soaking zone, then subdividing said stream into a plurality of streams having a total cross-sectional area not more than 0.75 times the otherwise unconsm'cted cross-sectional area of the stream,

6 whereby thermal currents in the stream are reduced and backward flow is prevented, the residence time of said stream in said soaking zone being at least about 5 minutes and insufiicient to produce excessive thermal degradation and discoloration of the product, thereby to produce a refined product having improved oxidation stability and freedom from corrosiveness to copper.

2. Process according to claim 1, wherein the liquid stream is passed alternately into an expanded zone and then subdivided into a plurality of subdivided streams.

3. Process according to claim 2, wherein the crosssectional area of the subdivided streams ranges from 0.5 to 50 percent of the unrestricted cross-sectional area of the stream.

References Cited in the file of this patent UNITED STATES PATENTS 1,915,592 Black et a1. July 27, 1933 2,001,899 Blair May 21, 1935 2,047,985 Weir July 21, 1936 2,846,356 Mills et a1. Aug. 5, 1958 

1. PROCESS FOR PRODUCING IMPROVED PETROLEUM PRODUCTS WHICH COMPRISES: CATALYTICALLY HYDROGENATING A PETROLEUM CHARGE STOCK TO PRODUCE A REFINE PRODUCT CONTAINING RELATIVELY NONVOLATILE CORROSIVE SULFUR-CONTAINING MATERIAL, SEPARATING THE REFINED PRODUCT FROM THE HYDROGENATION CATALYST, AND PASSING A STREAM OF THE SEPARATED REFINED PRODUCT IN LIQUID PHASE AT 450*F. TO 650*F. CONTINUOUSLY THROUGH A SOAKING ZONE, DISTRIBUTING SAID LIQUID STREAM IN AN EXPANDED AREA IN SAID SOAKING ZONE, THEN SUBDIVIDING SAID STREAM INTO A PLURALITY OF STREAMS HAVING A TOTAL CROSS-SECTIONAL AREA NOT MORE THAN 0.75 TIMES THE OTHER- 